Yakisugi - Burning Cypress timber
The process of Japanese burnt timber cladding starts off with choosing the right logs. When charring weatherboards it is important that you grade for straightness, grain density, and wood color.
The heat conditioning of Yakisugi is intense, upto 2200 degrees C to achieve the preferred level of char. The japanese burnt timber process strengthens the timber's cell structure through burning off cellulose whuich improves stability. Then the wood is drenched at just the right moment to finish the hardening.
After fire conditioning the wood can be used with heavy Char soot layer which is the best for a long life product, or brushed to knock down the soot layer in order to achieve the desired appearance.
Standard traditional products include Suyaki (original charred), Gendai (brushed once), and Pika-Pika (brushed twice).
How Yakisugi improves timber performance
The fire treatment improves the timbers characteristics and longevity by preventing decay and insect infestation, improving the dimensional stability, and interestingly improves fire resistance.
Yakisugi is a maintenance free exterior timber, that naturally resists environmental decay and evolves its beauty over time. Some people like to oil their Yakisugi charred timber every 5 years to maintain that new look.
Fungi and bugs
Timber is predominately structural lignin, with hemi-cellulose carbohydrates which are food for fungi and insects. Heat treatment of yakisugi burns off the cellulose, taking away much of the food and thus minimizes rot and bug infestation.
The fire treatment also hardens the outer layer of the timber. This combined with air drying, reduces dimensional movement in severe weather exposure.
Improved Fire resistance
The soot layer increases the temperature threshold needed for combustion, dramatically reducing flame spread, while also adding a hydrophobic protection against weathering.
All yakisugi timber starts as the sooty charred look of Suyaki. Timber is then brushed next to achieve the textural look of Gendai. Some customers may choose the refired and double brushed deep curves of Pika-Pika.
Suyaki’s thick soot layer will gradually become Gendai and last upto 50 years depending on burn quality and site weather conditions. The Gendai and Pika-Pika brushed surfaces will weather and color over time to a silvered look.